Direct link to user login page By default, the Login Page Form can always be found at:

http://www.mysite.com/?q=user.

Direct Link to User Registration Page

http://www.mysite.com/?q=user/register.

Direct link to Request Password Form

http://www.mysite.com/?q=user/password.

Search Form is build by the default template search-block-form.tpl.php copy paste it to your theme folder to customize it according to your needs.

comment-wrapper.tpl.php is the default template which provides an HTML container for the comments and comment.tpl.php is the default template for the individual comment. Copy paste both template to your theme folder and customize them according to your need. The comment form itself is generated by the comment_form() function which you can find in the file modules/comment/comment.module

User Login from is build with the user_login_block(), Which can be found in modules/user/user.module file

user_register_form() is used to generated user register form, this can be found in modules/user.module file

Thanks